The present invention relates generally to coating apparatus and, more particularly, to coating apparatus adapted to evenly and uniformly apply a coating material to a moving sheet of goods with little or no streaking.
In order to achieve an even and uniform application of a coating material on a moving sheet of goods, the amount of air which is introduced at the point of coating, i.e., the coating zone, must be minimized. An example of coating apparatus which is intended to eliminate or minimize the introduction of air into the coating zone is the apparatus described in U.S. Pat. No. 4,250,211. In the apparatus of this patent, the coating material emerges from a chamber or reservoir and is introduced into a coating zone through a slotted outlet port. The coating material is maintained under pressure in this coating zone.
The coating zone of the apparatus described in U.S Pat. No. 4,250,211 is bound or defined by the sheet of goods to be coated which is carried around a guide cylinder; an anterior throttle plate; the opening of the outlet port of the chamber; and a coating blade. The coating material emerges from the coating zone through a throttle slit which is created between the anterior throttle plate and the moving sheet of goods in a direction opposite the direction of the movement of the sheet. Such a configuration serves to reduce the amount of air which is introduced into the coating zone and, as such, is able to effect the coating operation relatively unimpeded by air pockets.
One of the inherent problems with such apparatus, however, is that the coating material tends to streak as it is applied to the sheet. This streaking is due to ripples which develop in the coating material within the coating zone. As can be readily appreciated, streaking of the coating material on the sheet of goods can prove commercially unacceptable.
Against the foregoing background, it is primary object of the present invention to provide coating apparatus which can uniformly and evenly apply a coating to a sheet of goods.
It is another object of the present invention to provide such coating apparatus where the amount of air which is introduced into the coating zone of the apparatus is minimized.
It is still another object of the present invention to provide such coating apparatus which will not streak the coating material on the sheet of goods to be coated.